1. Field of Invention
The invention relates to a lamp for use in an outdoor environment. In particular, the invention relates to a headlamp for a vehicle that includes a protective film located on a front lens of the vehicle headlamp and a method for making the vehicle headlamp. The film prevents mist, condensation or other haze from forming on the inside of the lamp chamber while also preventing discoloration of the front lens of the headlamp caused by UV light emitted from a light source located in the headlamp.
2. Discussion of Related Art
Conventional vehicle headlamps often include a lamp body that cooperates with a front lens formed of resin to form a lamp chamber. A discharge lamp bulb located within the lamp chamber acts as a light source. Typical discharge lamp bulbs for vehicle headlamps emit light containing UV light of great energy. This UV light tends to discolor the front lens and, after a period of time, causes the lens to be tinted yellow. In particular, lenses made of polycarbonate (PC) resin are frequently employed for the front lens of vehicle headlamps and are likely to be discolored upon irradiation with UV light.
In many conventional vehicle headlamps, a portion of the inner surface of the lamp body has a reflecting surface that is coated with an UV absorbing film formed of an UV absorbing material. The UV absorbing film prevents discoloration of the front lens.
In addition, many conventional headlamps include a second film or coating on the inner surface of the front lens. The second film or coating can be an anti-haze film formed of an anti-haze material that prevents the lamp chamber from being subjected to mist, condensation or other forms of haze. Examples of materials that can be used for the anti-haze material along with examples of the specific weight ratios and content descriptions of such materials are disclosed in Japanese Laid Open Patent No. 2-255854, which is incorporated herein by reference.
In the aforementioned conventional vehicle headlamp, the UV absorbing film for preventing discoloration of the front lens and the anti-haze film for preventing lamp chamber haze are separately applied to different portions of the inside of the lamp chamber. Therefore, the respective film coating processes have to be conducted separately and individually, which may complicate the overall lamp production process, increase the processing time, and thus result in an increased manufacturing cost.